Schottky diodes are employed in many applications due to their relatively low turn-on voltage (low forward voltage drop), and relatively fast switching times. Typical Schottky diodes have generally employed either low barrier height metals (e.g., titanium (Ti), titanium nitride (TiN), titanium silicide (TiSi2), cobalt (Co), cobalt silicide (CoSi2), etc.) or high barrier height metals (e.g., platinum (Pt), platinum silicide (PtSi), etc.) to form contacts over N-type silicon.
In many applications, low barrier height metal Schottky diodes have lower forward voltage drops than high barrier height metal Schottky diodes and are able to carry more current through a diode of a given size. However, low barrier height metal Schottky diodes generally allow greater current leakage when reverse biased (reverse leakage current) as compared to high barrier height metal Schottky diodes.
Various techniques have been employed to improve the leakage current characteristics in low barrier height metal Schottky diodes, such as to use relatively lightly doped N-wells. However, more lightly doped N-well Schottky diodes generally have higher resistances, so that their forward currents at a given bias are less than for a Schottky diode having a more highly doped N-well.
In certain applications it may be desirable for a Schottky diode to have a relatively small turn-on voltage, or forward voltage drop, and yet have a relatively small reverse leakage current.